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Digitale Medien

The generation of Mutator transposable element subfamilies in maize (1994)

Bennetzen, J. L. ; Springer, P. S.

Springer

Theoretical and applied genetics 87 (1994), S. 657-667

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ISSN: 1432-2242

Schlagwort(e): Transposable elements ; Mutation ; Evolution ; DNA repair ; Gene conversion

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract The mobile DNAs of the Mutator system of maize (Zea mays) are exceptional both in structure and diversity. So far, six subfamilies of Mu elements have been discovered; all Mu elements share highly conserved terminal inverted repeats (TIRs), but each sub-family is defined by internal sequences that are apparently unrelated to the internal sequences of any other Mu subfamily. The Mu1/Mu2 subfamily of elements was created by the acquisition of a portion of a standard maize gene (termed MRS-A) within two Mu TIRs. Beside the unusually long (185–359 bp) and diverse TIRs found on all of these elements, other direct and inverted repeats are often found either within the central portion of a Mu element or within a TIR. Our computer analyses have shown that sequence duplications (mostly short direct repeats interrupted by a few base pairs) are common in non-autonomous members of the Mutator, Ac/Ds, and Spm(En) systems. These duplications are often tightly associated with the element-internal end of the TIRs. Comparisons of Mu element sequences have indicated that they share more terminal components than previously reported; all subfamilies have at least the most terminal 215 bp, at one end or the other, of the 359-bp Mu5 TIR. These data suggest that many Mu element subfamilies were generated from a parental element that had termini like those of Mu5. With the Mu5 TIRs as a standard, it was possible to determine that elements like Mu4 could have had their unusual TIRs created through a three-step process involving (1) addition of sequences to interrupt one TIR, (2) formation of a stem-loop structure by one strand of the element, and (3) a subsequent DNA repair/gene conversion event that duplicated the insertion(s) within the other TIR. A similar repair/conversion extending from a TIR stem into loop DNA could explain the additional inverted repeat sequences added to the internal ends of the Mu4 and Mu7 TIRs. This same basic mechanism was found to be capable of generating new Mu element subfamilies. After endonucleolytic attack of the loop within the stem-loop structure, repair/conversion of the gap could occur as an intermolecular event to generate novel internal sequences and, therefore, a new Mu element subfamily. Evidence supporting and expanding this model of new Mu element subfamily creation was identified in the sequence of MRS-A.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00222890

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2

Digitale Medien

Genomic organization of the ribosomal DNA of sorghum and its close relatives (1989)

Springer, P. S. ; Zimmer, E. A. ; Bennetzen, J. L.

Springer

Theoretical and applied genetics 77 (1989), S. 844-850

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ISSN: 1432-2242

Schlagwort(e): Evolution ; Restriction fragment length polymorphism ; Grasses ; Maize ; Sugarcane

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary The structure and organization of the ribosomal DNA (rDNA) of sorghum (Sorghum bicolor) and several closely related grasses were determined by gel blot hybridization to cloned maize rDNA. Monocots of the genus Sorghum (sorghum, shattercane, Sudangrass, and Johnsongrass) and the genus Saccharum (sugarcane species) were observed to organize their rDNA as direct tandem repeats of several thousand rDNA monomer units. For the eight restriction enzymes and 14 cleavage sites examined, no variations were seen within all of the S. bicolor races and other Sorghum species investigated. Sorghum, maize, and sugarcane were observed to have very similar rDNA monomer sizes and restriction maps, befitting their close common ancestry. The restriction site variability seen between these three genera demonstrated that sorghum and sugarcane are more closely related to each other than either is to maize. Variation in rDNA monomer lengths were observed frequently within the Sorghum genus. These size variations were localized to the intergenic spacer region of the rDNA monomer. Unlike many maize inbreds, all inbred Sorghum diploids were found to contain only one rDNA monomer size in an individual plant. These results are discussed in light of the comparative timing, rates, and modes of evolutionary events in Sorghum and other grasses. Spacer size variation was found to provide a highly sensitive assay for the genetic contribution of different S. bicolor races and other Sorghum species to a Sorghum population.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00268337

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3

Digitale Medien

Structure and evolution of the genomes ofsorghum bicolor andZea mays (1993)

Berhan, A. Melake ; Hulbert, S. H. ; Butler, L. G. ; [weitere]

Springer

Theoretical and applied genetics 86 (1993), S. 598-604

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ISSN: 1432-2242

Schlagwort(e): Maize-Sorghum-Restriction fragment length polymorphism ; Genetic maps ; Inversion ; Translocation ; Duplication

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Cloned maize genes and random maize genomic fragments were used to construct a genetic map of sorghum and to compare the structure of the maize and sorghum genomes. Most (266/280) of the maize DNA fragments hybridized to sorghum DNA and 145 of them detected polymorphisms. The segregation of 111 markers was analyzed in 55 F2 progeny. A genetic map was generated with 96 loci arranged in 15 linkage groups spanning 709 map units. Comparative genetic mapping of sorghum and maize is complicated by the fact that many loci are duplicated, often making the identification of orthologous sequences ambiguous. Relative map positions of probes which detect only a single locus in both species indicated that multiple rearrangements have occurred since their divergence, but that many chromosomal segments have conserved synteny. Some sorghum linkage groups were found to be composed of sequences that detect loci on two different maize chromosomes. The two maize chromosomes to which these loci mapped were generally those which commonly share duplicated sequences. Evolutionary models and implications are discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00838715

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Digitale Medien

The Rp3 disease resistance gene of maize: mapping and characterization of introgressed alleles (1995)

Sanz-Alferez, S. ; Richter, T. E. ; Hulbert, S. H. ; [weitere]

Springer

Theoretical and applied genetics 91 (1995), S. 25-32

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ISSN: 1432-2242

Schlagwort(e): Restriction fragment length polymorphism ; Near-isogenic lines ; Puccinia sorghi ; Introgression ; Gene duplication

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract The Rp3 locus of maize conditions race-specific resistance to a fungal rust pathogen, Puccinia sorghi. Both morphological and DNA markers were employed to characterize alleles of Rp3 and to accurately position Rp3 on the maize genetic map. DNA marker polymorphisms distinctive to each Rp3 allele were identified, allowing the identification of specific Rp3 alleles in cases where rust races that differentiate particular alleles are not available. In a population of 427 progeny, Rp3 and Rg1 were found to be completely linked, while Lg3 was approximately 3 cM proximal on the long arm of chromosome 3. In this same population, 12 RFLP markers were mapped relative to Rp3; the closest markers were UMC102 (about 1cM distal to Rp1) and NPI114 (1–2 cM proximal). These and additional DNA probes were used to characterize the nature and extent of flanking DNA that was carried along when six different Rp3 alleles were backcrossed into a single background. Depending upon the allele investigated, a minimum of 2–10cM of polymorphic DNA flanking the Rp3 locus was retained through the introgression process. In addition, many of the probes that map near Rp3 were found to detect an additional fragment in the Rp3 region, indicating that portions of this chromosomal segment have been tendemly duplicated. The materials and results generated will permit marker-assisted entry of Rp3 into different maize backgrounds and lay the foundation for the eventual map-based cloning of Rp3.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00220854

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5

Digitale Medien

Concomitant regulation of Mu1 transposition and Mutator activity in maize (1987)

Bennetzen, J. L. ; Fracasso, R. P. ; Morris, D. W. ; [weitere]

Springer

Molecular genetics and genomics 208 (1987), S. 57-62

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ISSN: 1617-4623

Schlagwort(e): Transposable elements ; Mutation ; Mutator ; Maize

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary The mutagenic activity of the maize transposable element system Mutator can be lost by outcrossing to standard, non-Mutator lines or by repetitive intercrossing of genetically diverse Mutator lines. Lines losing Mutator mutagenic activity in either manner retain high copy numbers (10–15 per diploid genome) of the Mutator-associated Mu transposable elements. Frequent transposition of Mu1-related elements is observed only in active Mutator lines, however. The loss of Mutator activity on intercrossing is correlated with an increase in the copy number of Mu1-like elements to 40–50 per diploid genome, implying a self-encoded or self-activated negative regulator of Mu1 transposition. The outcross loss of Mutator activity is only weakly correlated with a low Mu element copy number and may be due to the loss of a positive regulatory factor encoded by a subset of Mu1-like elements. Transposition of Mu elements in active Mutator lines generates multiple new genomic positions for about half the elements each plant generation. The appearance of Mu1-like elements in these new positions is not accompanied by equally high germinal reversion frequencies, suggesting that Mu1 may commonly transpose via a DNA replicative process.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00330422

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6

Digitale Medien

Complex duplications in maize lines (1993)

Hong, K. S. ; Richter, T. E. ; Bennetzen, J. L. ; [weitere]

Springer

Molecular genetics and genomics 239 (1993), S. 115-121

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ISSN: 1617-4623

Schlagwort(e): RFLP ; Disease resistance ; Duplicated sequence ; Recombination ; Linked repeats ; Hypervariable loci

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Rp1 is a disease resistance complex and is the terminal morphological marker on the short arm of maize chromosome 10. Several restriction fragment length polymorphisms (RFLPs), which map within 5 map units of Rp1, were examined to determine if they are also complex in structure. Two RFLP loci, which mapped distally to Rp1, BNL3.04 and PIO200075, existed in a single copy in all maize lines examined. These two loci cosegregated perfectly in 130 test cross progeny. Two RFLP loci that map proximally to Rp1 had unusual structures, which have not yet been reported for maize RFLPs; the loci were complex, with variable numbers of copies in different maize lines. One of the loci, NPI285, occasionally recombined in meiosis to yield changes in the number of copies of sequences homologous to the probe. The other proximal locus, detected by the probes NPI422, KSU3, and KSU4, was relatively stable in meiosis and no changes in the number of restriction fragments were observed. The similarity in map position between Rp1 and the complex RFLP loci indicate there may be genomic areas where variable numbers of repeated sequences are common. The structure of these complex loci may provide insight into the structure and evolution of Rp1.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00281609

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